Rotary compressor valve



Nov. 5, 1957 R. E. BOSCH ET AL 2,812,123

ROTARY COMPRESSOR VALVE Filed Nov. 25, 1955 INVENTORS. ROBERT E. 50504 &KENNETH K. COOPER THEIR ATTORNEY United States Patent 2,812,128 ROTARYCOMPRESSOR VALVE Robert E. Bosch, West Caldwell, andKennetll K. Cooper,North Caldwell, N. J., assignors to General Electric Company, acorporation'of New York Application November 25, 1955, Serial No.548,887

Claims. (31. 230-138) T hepresent invention relates generally to rotarypumps and is more specifically concerned with a variable displacementrotary pump or compressor particularly adapted for use in refrigeratingsystems and the like.

. For various reasons,.it is desirable that the compressors employed forcompressing gases, such as those used in refrigeration systems, becapable of operating at one displacement or output level under certainconditions and at higher or lower displacements under certain otherconditions. For example, it is frequently desirable to unload orpartially unload such compressors during the starting operation in orderto reduce the load on the compressor driving means. Alsoin the operationof reversible refrigcrating systems or heat pumps, the most efficientoperationlthereof is obtained when refrigerant flow rate through thesystem is-higher under conditions of operation in which the ambienttemperature at the evaporator is low thanunder other operatingconditions in which the evaporator ambient temperature is relativelyhigh. In other words, for optimum performance a relatively highrefrigerant flow rate, which can be obtained by a compressor having arelatively high displacement, is desirable when the heat pump isoperating on the heating cycle and the outdoor temperature is low and asomewhat lower refrigerant flow rate or compressor displacement is mostefficient when the heat pump is operating either on the cooling cycle oron the heating cycle at relatively high outdoor temperatures. 7

In the copending application of Kenneth K. Cooper, Serial No. 548,810,filed concurrently herewith and assigned to the same assignee as thepresent invention, there is broadly described and claimed amulti-chamber rotary compressor including suction valve control meansfor varying the compressor displacement. The present invention, which isan improvement over the prior invention of the Cooper application, hasas a primary object the provision of an improved suction valvearrangement for varying the displacement of va multi-chamber rotarycompressor.

Further objects and advantages of the invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize the invention will be pointed out with particularity in theclaims annexed to and forming part of this specification.

In carrying out the objects of the present invention, there is provideda rotary compressor including a plu rality of movable vanes engaging theperiphery of the compressor rotor and-dividing the compressor" cylinderinto a plurality of pumping chambers. Each of the chambers is providedwithvalve-controlled suction and discharge ports communicating with therespective chambers. In order to provide for variable displacementoperation of the compressor, at least one of the suction ports 2,812,128Patented Nov. 5, 1957 2 position in which the valve member covers andcontrols the suction inlet and a position in which the inlet is open.Maximum displacement of the compressor or pump is obtained when thesuction valve member overlies the inlet and operates between open andclosed positions in response to pressure conditions within the chambersserved by the valve while a lower-output or displacement is ob: taineclwhen the suction valve is rendered inoperable in an open position.

For a better understanding of the invention reference may-be had to theaccompanying drawings in which Fig. 1 is a schematic viewillustrating'an embodiment of the present invention; and

Fig. 2 is a view similar to Fig. 1 illustrating the positionof thecompressor components under diiferent operating conditions.

Referring to Fig. 1 of the drawing, there is shown an embodiment of thepresent invention in the form of a rotary compressor 1 as part of ahermetically sealed compressor unit for a refrigerating system. The pumpis therefore disposed Within a sealed casing 2 which also contains amotor (not shown) for driving the compressor. The pump includes ahousing 3 having therein a cylinder 4 in which is rotatably andeccentrically mounted a rotor 5. The rotor 5 is mounted on a drive shaft'6 concentrically disposed within the cylinder 4 and connected to thedriving motor. The housing 3 is provided with diametrically opposedslots 7 and 8 which open into the cylinder 4 and receive a pair ofmovable vanes 11 and 12 engaging the rotor 5 and dividing the cylinder 4into a plurality of pumping chambers 14 and 15. Springs 16 disposed.within the slots '7 and 8 behind the respective vanes 11 and 12 :serveto bias-the vanes into continuous contact with the rotor 5 during itseccentric rotation within the cylinder 4. r

- Eachof the chambers is also provided with spacedapart inlet or suctionports and outlet or discharge ports, the relative ,positions of theseports in the chamber depending upon thedirection of rotation of therotor 5. When the rotor-is driven or rotated in a clockwise directionasillustrated in the drawing, the suction port gen-- erally indicated bythe numeral 17 for the chamber 14 is positioned immediately adjacent thevane 11 at-the leading end of the chamber while the discharge port 18for this chamberis positioned at the trailing end of the chamberimmediately ahead of the vane 12. In the same manner, the chamber 15 isserved by a communicating suction port .19 immediately following thevane 12 and a communicating discharge port 20 at the opposite end of thechamber immediately preceding the vane 11. Valve means are provided forcontrolling the inlets to each of the ports and in the illustratedembodiment ofthe invention these valvemembers are composed of springmaterial such as spring steel. The valvemembers for the suction ports 17and 19 are respectively indicated by the numerals .21 and. 22 while thevalve members for the discharge ports 18 and 2d are respectivelyindicated by the numerals 24 and 25.

, With particular reference to Fig. .1, the arrangement thus'fardescribed comprises ,a rotary compressor strucrure which, because of thepresence of more than one vane and :pumping chamber, has a higherdisplacement bers 14 and 15 operate independently of one another..

The fluid to be compressed is drawn into the chamber 14 through thesuction port 17 served by the suction inlet 27 and is discharged throughthe discharge port 18 into the interior of the easing 2 while fluidintroduced into the chamber 15 through the suction port 19 served by thesuction inlet 28 is discharged from this chamber through the dischargeport 20 which also communicates with the interior of the casing 2. It isto be understood that, in the illustrated application of the compressor,the lines to suction inlets 27 and 28 are connected to the evaporator ofa refrigerating system when the compressor of the present invention isemployed in such a system and that the compressed refrigerant introducedinto the interior of the casing 2 from the discharge ports 18 and 20flows from the casing through the-discharge line 30 to the condenser, ofthat refrigerating system.

The operation of the compressor may best be described with reference tothe travel of the point P representing the point on the rotor which isin contact with, or closely adjacent, the wall of the cylinder 4.

In considering the operation of the compressor, it should be noted thatboth chambers go through the same operating cycle, the cycle for onechamber lagging the cycle for the other chamber by 180 when thecompressor is provided with two vanes 11 and 12. With the point P in theposition shown in Fig. 1 of the drawing, the upper chamber 14 hasreached its maximum volume or displacement position following anexpanding period during which gas has been drawn from the suction port17 into this chamber and this volume represents one half of the totalmaximum displacement for a two chamber compressor. As the rotor movespast this point, the volume of chamber 14 will continue to decreaseuntil the point P has reached a position opposite or closely adjacentthe discharge port 18, at which point all of the fluid which has beendrawn into the chamber 14 will have been discharged through thedischarge port 18.

Again referring to Fig. l, the position of the rotor relative to thelower chamber 15 illustrates another point in the operating cycle. Inthis position of the rotor, the chamber 15 may be said to be dividedinto two portions, one on each side of the point P. The portion 15awhich is decreasing in size contains compressed fluid being dischargedthrough the port 20 while the portion 15b which is expanding and willcontinue to expand until it reaches a volume comparable to thatillustrated for chamber 14 is drawing suction gas through the suctionport 19. Since the various valve members and particularly the valvemembers 21 and 22 open and close depending upon pressure conditionswithin the chambers served thereby or, more specifically, the pressuredifferences on opposite sides of these valve members, it will be seenthat when a chamber reaches its maximum volume following the suctionportion of the cycle and enters the compressor portion of the cycle, thesuction valve members will close and remain closed until the particularchamber again enters a suction portion of the cycle. As a result, thedis placement or maximum displacement of each of the chambers isrepresented by the volume or maximum volume of the chamber at the timethat the suction valve feeding that chamber closes following a suctionportion of the cycle. In other words, the chamber 14 as illustrated inFig. l is full of suction fluid or gas and represents the totaldisplacement of this chamber for one revolution of the rotor 5. As therotor continues to rotate, the suction valve 21 closes and prevents thegas or fluid contained therein from re-entering the suction inlet 27 sothat all of this gas will be discharged through the discharge port 18.Since the chamber 15 goes through the same cycle of operation as chamber14 during each revolution of the rotor 5 and has the same displacementas the chamber 14, the total displacement of the compressor for eachrevolution'of the rotor is equal to the combined total displacement ofthe plurality of chambers or, in the case of a twochamber compressor,twice the volume of the chamber 14 as illustrated in Fig. '1.

In the illustrated modification of the invention, the suction ports 17and 18 are in the form of slots in the peripheral wall of, the housing 1communicating at their inner ends with the cylinder 4, or morespecifically the respective chambers which they serve and the suctioninlets 27 and 28 enter a side wall of the slots near their open ends.Slidably disposed within each of the slots is a valve supporting member29 and the spring steel valve members 21, 22 are respectively fastenedat one end thereof to the valve support members, each of which havesloping side portions 32 forming valve backing surfaces for the free oroperating ends of the valve members 21, 22. The valve support membersand therefore the flexible valve members attached thereto are free tomove within the port slots 17 and 19 between a forward position in whichthe flexible end portions of the valve members 21, 22 overlie theirrespective inlets 27, 28 as shown in Fig. 1 and a withdrawn or recessedposition in which the inlets 27, 28 are open in all positions of therotor 5, or in other Words, not controlled by the valve members.

Tension springs 33 suitably attached to the valve support members andthe bottom walls 35 of the port slots 17, 18 bias the valve supportmembers to the retracted or withdrawn position in which the valvemembers clear inlets 27, 28 and a pin and slot arrangement, generallyindicated by numeral 39, limit the movement of the valve supportingmembers in either direction.

In order to overcome the biasing action of the springs 33 and to permitthe suction valve members to operate in response to pressure conditionswithin the chambers and close their respective suction port inletswhenever the pressures within the chambers served by these ports arehigher than the suction gas pressure within the suction supply lines 27and 28, a control fluid is introduced through lines 36 into the cylinder38 behind the valve support members 29. This control fluid is preferablyat a pressure greater than the pressure within the suction lines 27 and28 and serves to move the valve supports forwardly so that the suctionvalve members will overlie the inlets 27, 28 and move between Open andport sealing positions in accordance with changing pressure conditionswithin the pump chambers.

The control fluid introduced into the cylinders 38 may be high pressuredischarge gas from the discharge line 30 with the flow of the controlfluid being regulated by means of a valve 37, although it is to beunderstood that the present invention is not restricted to any specificmeans for rendering the suction valves operable or inoperable or to aparticular source of the control fluid or gas. For example in thehermetic compressor of the type shown in the drawing which normallycontains a body of lubricating oil, this oil at compressor dischargepressure may be employed to effect movement of the valve support members29. Alternatively the control may be by means completely separate orauxiliary to the system of which the pump forms a part. Likewise, it isto be understood that while a single means, such as valve 37, has beenshown for controlling the operation of both of the support members forthe suction valves 21 and 22, separate control means may be employed sothat either one or both of the suction valves can be rendered operableor inoperable as to the respective inlets 27, 28 thereby providing acompressor having three different output levels.

The operation of the compressor at less than its maximum displacement,or more specifically at the displacement obtained when both the pressureis relieved in cylinders 38 and the suction valves are withdrawn to aninlet open position by springs 33, will best be understood by referenceto Fig. 2 of the drawing. In this figure the rotor is shown in aposition in which the point P is in contact with the vane 11 and isabout to close 01? the suction port 17. With the suction valves in anopen position, a portion of the suction gas drawn into each cylinderduring part of the cycle is returned through the suction port before thepump enters the compression portion of the cycle. This return of part ofthe suction gas drawn into the chamber occurs as the rotor point P movesthrough an angle of ninety degrees from: a position" such as thatillustrated in Fig. v1 to the position illustrated in Fig. 2. As asignificant portion of the gas drawn into the chamber 14 up to the pointwhere it attained its maximum volume as shown in Fig. 1 has been"returned through the open suction port 17 and inlet 27, only theremaining volume of gas represented by the area of chamber 14 in Fig. 2is discharged through the discharge port 18. Thus the chamber volumerepresenting the maximum chamber displacement when the suction valve isinoperable is that represented by the volume of the cylinder 14 when therotor point P is in a position close to that shown in Fig. 2 and inwhich is first sealed the suction port 17. In other words, the volume ofthe chamber 14 as shown in Fig. 2 represents the relative displacementof the pump during operation with the suction valves in retracted orinoperable position while the volume of the chamber 14 as illustrated inFig. 1 represents the relative displacement of the pump when the suctionvalves operate in the usual manner, i. e., in response to pressureconditions within the chamber. Of course, since chamber 15 functions inthe same manner as chamber 14, the actual total displacement of the pumpis equal to the combined displacement of the chambers under eitherset ofoperating conditions. An intermediate displacement is, of course,obtained when only one of the two suction valves is inoperative and theremaining valve operates in the usual manner.

'From the foregoing it will be seen that there has been provided inaccordance with the present invention a rotary pump or compressor havingat least three steps of displacement. While the advantages of such apump for various applications may be obvious, it should perhaps be notedthat it is particularly useful in connection with refrigeration systems.For example if valve 37 is of the normally open type, and is used asshown to control the flow of discharge gas from the discharge line 30 tothe suction valve control cylinders, the invention makes provisions forstarting the compressor in a partially loaded state since thedischargepressure in line 30 is then low and the valves 21 and 22 aretherefore held in an open position by the respective springs 33 actingon support members 29. As the pressure in the ,discharge line 30increases, the biasing action of the springs 35 will be overcome by theincreasing pressure of the discharge gas until finally the supportingmembers move inwardly to a point where the suction valves overlie theinlets 27, 28 and the valves open and close to control the passage ofgas through the inlets depending only upon the pressure conditionswithin the chambers served thereby. Alternatively, the valve 37 can becontrolled by pressure or temperature conditions within or as a functionof some other portion of a refrigerating system, for example byevaporator pressure or temperature or other suitable control means sothat for example the rotary compressor will operate at a lowdisplacement level with the suction valves open under certain operatingconditions and under other conditions at a higher displacement with thecontrol suction valves operable.

While there has been shown and described some specific embodiments ofthe invention, it is not desired that the invention be limited to theparticular construction shown and described and it is intended by theappended claims to cover all modifications within the spirit and scopeof the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A rotary compressor comprising a housing having a cylinder therein, arotor eccentrically mounted with said cylinder, a plurality of movablevanes engaging the periphery of said rotor and dividing said cylinderinto a plurality of chambers, suction and discharge ports for eachchamber, each of said suction ports comprising a slot in said housingcommunicating with one of said chambers, a suction inlet in a side wallof said slot, a valve support member slidably disposed in said slot, aflexiblevalve having one end secured to said supporting member inparallel relationship to said side wall, said support member beingmovable in said slot between a position in which the free end of saidflexible valve is in an operative position relative to said suctioninlet and a position in which said inlet is always open for allpositions of the rotor,

and means for effecting movement of said support memher to each of saidpositions.

2. A rotary compressor comprising ahousing having a cylinder therein, arotor eccentrically mounted within said cylinder, a plurality of movablevanes engaging the periphery of said rotor and dividing said cylinderinto a plurality of chambers, suction and discharge ports for eachchamber, each of said suction ports comprising a slot in said housingcommunicating with one of said chambers, a suction inlet in a side wallof said slot, a valve support member slidably disposed in said slot, aflexible valve having one end secured to said support member, saidsupport member being movable in said slot between a position in whichthe free end of said flexible v-alve overlies said suction inlet and aposition in which said inlet is always open for all positions of saidrotor, means biasing said support member to one of said positions andmeans operable to move said support member to the other of saidpositions.

3. A rotary compressor comprising a housinghaving a cylinder therein, arotor eccentrically mounted within said cylinder, a plurality of movablevanes engaging the periphery of said rotor and dividing said cylinderinto a plurality of chambers, suction and discharge ports for eachchamber, each of said suction ports comprising a radially-extending slotin said housing communicating with one of said chambers, a suction inletin a side wall of said slot, a valve support member slidably disposed insaid slot and having a flexible valve mounted thereon, said supportmember being movable in said slot between a position in which saidflexible valve overlies said suction inlet and a position in which saidinlet is always open for all positions of the rotor, means biasing saidsupport member to one of said positions and means for moving saidsupport member to the other of said positions.

4. A rotary compressor comprising a housing having a cylinder therein, arotor eccentrically mounted within said cylinder, a plurality of movablevanes engaging the periphery of said rotor and dividing said cylinderinto a plurality of chambers, suction and discharge ports for eachchamber, each of said suction ports comprising a radially-extending slotin said housing communicating with one of said chambers, a suction inletin a side Wall of said slot, a valve support member slidably disposed insaid slot and having a flexible valve mounted thereon, said supportmember being movable in said slot between a position in which saidflexible valve covers said suction inlet and a position in which saidinlet is always open for all positions of said rotor, spring meansbiasing said support member rearwardly in said slot to an inlet openposition and means operable to move said support member in a forwarddirection to a position in which said valve overlies said suction inlet.

5. A rotary compressor comprising a housing having a cylinder therein, arotor eccentrically mounted within said cylinder, a plurality of movablevanes engaging the periphery of said rotor and dividing said cylinderinto a plurality of chambers, suction and discharge ports for eachchamber, each of said suction ports comprising a slot in said housingcommunicating with one of said chambers, a suction inlet in a side wallof said slot, a valve support member slidably disposed in said slot andhaving a thin flexible valve attached thereto at one end, said supportmember being movable in said slot between a position in which the freeend of said flexible valve covers said suction inlet and a position inwhich said inlet is always open forall positions of said rotor, springmeans biasing said support member to an inlet open position foroperation of saidcompressor at-one displacement and'means operabletoMOVCSQidSUPPOITlHCIHbBI to a positionin which said valve overlies saidsuction inlet forop'erationdf said compressor at a high displacement.

References Cited inthelfile of thispatent UNITED STATES PATENTS 711,092Bates oct. 1'4, 1902 -8 Bidw' ell Aug. 8, 1922 Bi'clwell Aug.. 22, 1922Monk M211. 9, 1926 Ruckstuhl n. Feb. 8, 1927 Smith Ian. 24, 1956

